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Chemical Communication


The sound and the volatiles and a fly queen serving face

by Emily Harwitz
October 9, 2021 | A version of this story appeared in Volume 99, Issue 37


The sound of bug smells

A sawfly larvae holds a boombox
Credit: Jean-Luc Boeve/Yang H. Ku/C&EN/Shutterstock
Bugging out: Scientists translated sawfly larvae's repellent smells into sounds.

A human volunteer stands in a room furnished with a speaker. Sounds begin to play that are so unpleasant that the human steps back to move away. The sounds are eerie and conjure otherworldly beings, but these sounds actually originate a lot closer to Earth. They’re the volatile chemicals emitted by sawfly larvae to scare off predatory ants—translated into sound. And it turns out that humans are repelled by the odors’ translated sounds just as much as ants are repelled by the smell of them (Patterns 2021, DOI: 10.1016/j.patter.2021.100352).

Jean-Luc Boevé of the Royal Belgian Institute of Natural Sciences, who led the study, is interested in the chemical ecology of insects, including the defensive chemicals they emit to ward off predators. Those chemicals can be challenging to study, though. Sometimes insects produce vanishingly small amounts of the volatiles, or the insects themselves are hard to find. Boevé wondered if there could be another way to measure the bioactivity of these chemicals without having to collect large amounts from the insects themselves.

As an amateur composer and pianist, Boevé is also interested in sounds. The perception of a sound, like a smell, has a climax and then tapers off. Boevé thought that maybe the acrid insect chemicals could be mapped to sounds. To test this, Boevé and a colleague harvested volatile chemicals from sawfly larvae and observed how predatory ants reacted to the odors. Then, after chemically profiling secretions from 16 sawfly larvae species, the researchers mapped chemical traits, like molecular weight, to sound traits, like pitch, duration, and frequency. Then they used a synthesizer to create the sounds. The result was a library of chemical compounds and species-specific soundtracks plus the sounds of 20 individual molecules found in the secretions.

The researchers played the sounds to human subjects and measured how quickly and how far the humans moved away from the speaker. Boevé compared humans’ reactions to the sounds to ants’ reactions to the smells and says he was “quite surprised” to find them statistically correlated.

“The whole paper is a proof of concept,” Boevé tells Newscripts, and the takeaway message is that “it seems to be an adequate method to study the chemical ecology of insect-predator relationships, so it should be continued by other studies.”


Category is: Flies!

RuPaul in metallic purple dress next to the metallic rainbow Opaluma rupaul fly
Credit: World of Wonder (RuPaul); Bryan Lessard/CSIRO (fly)
Fly pride: RuPaul inspired the name for this rainbow-hued fly.

One recent night, after a long day of writing species descriptions of invertebrates new to Western science, Australian entomologist Bryan Lessard, also known as Bry the Fly Guy, sat down to watch RuPaul’s Drag Race—a reality show competition to find the most glamorous drag queen. Seeing the drag queens’ fabulous looks made Lessard think about a metallic rainbow fly that had blown him away earlier with its beauty. “It was literally dressed in the pride flag, and I thought, ‘You know what? I’m going to name this after RuPaul because it is a fierce queen of the fly world,’ ” Lessard tells Newscripts. “They look like little beautiful jewels buzzing around on the forest floor, and they have legs for days just like RuPaul.” And thus, Opaluma rupaul was officially named.

Lessard, who works at CSIRO’s Australian National Insect Collection, also got to choose the new genus name Opaluma. “Opa” is Latin for Australia’s famed dazzling opals. “Luma” is Latin for “thorn” because the flies have a thorn tucked under their abdomen, which is what defines this genus. “Drag queens are known for tucking,” Lessard says, referring to ways that drag queens disguise a crotch bulge, “so I thought it was definitely appropriate.”

By naming the fly after a globally renowned pop culture icon, Lessard hopes to bring attention to the plight of these neglected and disappearing species. Flies are some of the most important pollinators of native plants and crops. They recycle nutrients by turning leaf litter into compost. They’re a vital part of other creatures’ diets. And, Lessard says, “they have personalities. It’s so cute seeing some of these flies in the rain forest just dancing around for each other’s attention and playing with each other in the air.”

And by naming the fly after a gay icon, Lessard, who is gay, wants to send a message to other members of the LGBTQ+ science community that “we’re allowed and we’re here and we’re queer,” he says.

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